The invention relates to a detection system for detecting optical particles, the system comprising a transparent slide, a composition arranged on the slide, a light source able to light the composition and the slide, and a device for acquiring at least one image of the composition lit by the light source, the transparent slide being positioned between the light source and the acquisition device.
The optical particle detection composition comprises water, the particles and a surfactant, the particles having a diameter preferably smaller than 10 μm and in particular a diameter smaller than 1 μm, the surfactant having a concentration preferably at least equal to the critical micellar concentration (CMC).
The invention also relates to a method for detecting optical particles using such an optical detection system.
The invention in particular applies to the detection of micrometric and sub-micrometric particles, in particular biological particles, such as cells, bacteria or viruses. The invention also applies to the detection of particles in the form of microbeads.
A detection system of the aforementioned type is known from document WO 2011/045360 A1. The composition comprises micrometric or sub-micrometric particles or organisms, water and a wetting agent, such as polyoxyethylene 20 sorbitan monolaurate, also known under the commercial name TWEEN 20.
This composition is deposited in the form of a drop on the transparent slide, and images of the drop are acquired during its evaporation. When the drop evaporates, the formation of a film on the surface of the particle is observed, and that residual film, covering the particle, serves as a micro-lens, which makes it possible to improve the detection of the particle.
However, such a detection system does not allow easy detection of particles with a size smaller than a micrometer. In fact, below that size, the signal-to-noise ratio decreases.